Process for stabilizing or deactivating sludges, precipitates, and residues occurring or used in the manufacture of tetraalkyl leads



Patented Sept. 10, 1946 PROCESS FOR STABILIZINGOR DEACTIVAT- ING' SLUDGES, PRECIPITATES, AND RESI- DUES OCCURRING OR USEDIN THEQMAN- UFACTU-RE OF TETRAALKYL LEADS Adrian L. Linch, Wilmington; DeL', assignor to E. I. du- Pont de Nemours & Company, Wilmin'gton', Del., a corporation of. Delaware No'Drawingr Application September 116, 1942, Serial No. 458,582

8' Claims. I

'I'h'is'invention' relates to a process for stabiliz ing or deactivating'slud'ges; precipitates and residuesoccurring or used in the manufacture of tetraalkyl leads, and which normally tend to promote decomposition andigni'tion. of the tetraalkyl leads that mayibe' contained therein.

It is known that alk'yl metal compounds in general are quite unstable and decompose readily, particularly in the presence of air or oxygen. It has also been found that these alkyl metal compounds are particularly unstable when adsorbed on material whichpresent a large surface area per unitvolume such as silica gel, clays, alumina, earths, asbestos; charcoal, and materials of similar structure which materials appear to exert a catalytic effect in the: decomposition of. these alkyl metal compounds. Even tetraalkyl leads such as tetraethyl lead which i known to be somewhat more stable than some of the other alkyl. metal compounds decomposes andoften ignites in the presence of oxygen when small amountsare' adsorbed on materials that offer. extended surface areas, particularly when the masses: containing. the tetraethyl lead are exposed to temperatures somewhat higher than normal atmospheric temperatures; The tend encyto' oxidize and ignite, of course; varies with the substancewith which. the alkyl metal compound i incorporated, some materials apparent 1y exerting a greater catalytic effect than. others in promoting ignition of the alkyllead com-- pounds In the manufacture of tetraalkyl leads, such 1 amounts, finally are deposited as sludges in the pipe's'and tanks and other processing equipment, and these sludge wh'ich contain tetraethyl lead adsorbed therein when exposed to oxygen or air 1 often ignite; thus presenting-serious ignition and explosion hazards in the process.

Methods have been advanced forthe removal of practically all the sludge" forming materials from the tetraethyl lead" after its distillation, such as by controlled blowing with air or oxygen with agitation, preferably" under a layer of wa--" ter, followed by separation of the precipitated sludge, as more particularly described in copending application Ser. No. 393,680; However, evenin these cases the sludges which are deposited by the" action of. the oxidizing agent and which invariably contain tetraethyl lead, tend to ignite when. exposed to air thus presenting. serious ignition hazards, making it desirabl that even these sludges should be deactivated. during. their formation'or afterwards to permit of their removal anddi'sposal in a safe manner.

It is. therefore an object of thisinvention' to provide'a process for stabilizing sludges, precipitates: and residues occurring in: the manufacture of tetraalkyl lead compounds whereby the ignition hazard presented by the lead alkyl com pound in contact with: such catalytic surfaces. is reduced. or completely overcome.

It is a still further object of the invention to render inactive. materials-which. tend to exert a catalytic. effect in the decomposition of tetraalkyl leads in the presence of air thus permitting the safe use of such materials as filter aids, in the manufactureof tetraalkyl lead.

I have found that sludges, precipitates and res-- idues occurring or involved in the production of tetraalkyl. lead which ofier large surface areas per unit: volumeand whichnormally tend to exert catalytic eifect and causedecomposition and-ignitionv of. the? tetraalkyl lead: whichmay. be: con.- tain'edtherein can be renderedinactive convem iently'and economically by washingor otherwise treating them with solutions. or: dispersions of oil soluble-copper or iron salts of organic carboxylic acids; appear tobe preferentiallyabsorbed by the active materials; which materialsretain their capacity to absorb the tetraalkyl lead, although-they no longer have the property of inducing ignition of the tetraalkyl lead absorbed therein.

By the terms sludges, precipitates and residues I include-thosefilte'r aids which may be employed in the production of the tetraalkyl leads and whichofier a large surfacea'rea per unit volume and" are known to accelerate decomposition of the'tetraalkyl leads onexposure to air or oxygensuch as clays, silica, earths, charcoal, etc. These filter aid's are rendered inactive by treating them with copper or iron salts of organic carboxylic acids either before or after they are employed in the process. The effectiveness of these copper" or iron salts in the deactivation of these active materials is not materially reduced by washing the deactivated materials with Water or other solvents or by drying them down prior to use.

The copper or iron salts of organic carboxylic The'se' stabilizing or deactivating agents acids, being oil soluble compounds, may be dissolved directly in the tetraalkyl lead before the sludge is precipitated by the method more particularly described in copending application Ser. No. 393,680. They may be added to the tetraalkyl lead after the sludge has been precipitated but before the tetraalkyl lead and sludge are separated; they may be added to a slurry of the tetraalkyl lead and sludge; or they may be dissolved in a suitable solvent and agitated with the separated sludge. These deactivators may be employed as a dispersion or a suspension in any type of solvent that may be desired for use in the treating of the tetraalkyl lead.

In general, the quantity of stabilizing agent required will be from about 1 to based on the dry weight of the active material to be treated so that in the treatment of the sludges occurring in or to be precipitated from the crude tetraethyl lead in the usual methods of manufacture in which there are usually not more than two parts of precipitated sludge obtainable from the 1,000 part of crude tetraethyl lead, it has been found that if 0.1 to 0.2 part of the stabilizing agents be employed per 1,000 parts of crude tetraethyl lead the sludges precipitated therefrom will be stabilized and when dried or heated will not cause ignition of the tetraethyl lead that may be contained therein. The amount of deactivator employed may, of course, be varied over a wide range. Good results have been obtained with concentrations as low as 0.05% of the deactivator based on the weight of the dry active material. While amounts as high as 100% based on the dry weight of the active material may be employed, the use of excessively large amounts over that actually required to deactivate the active material merely contributes unnecessarily to the cost of the process and serves no useful purpose.

In treating dry materials such as the filtered tetraethyl lead sludge, filter aids or the like, the quantity of stabilizing agent required may be dissolved in a suitable solvent. Good results have been obtained with solutions of the deactivator of concentrations as low as 0.05%. The upper limit of concentration will, of course, usually be determined by the solubility of the deactivator in the particular solvent employed. It is, of' course, advantageous to employ a sufiicient amount of solution to insure complete contact with all the material to be deactivated. If dispersions or suspensions of the deactivator are used, it will be found advisable to employ somewhat larger quantities and concentrations in order to insure adequate contact between the active material and the stabilizing agent within a reasonable time.

Where the sludges or precipitates settle out in the pipe lines or other processing equipment during the manufacture or purification of the tetraalkyl leads, they may be deactivated, to insure safety in their removal or during repair of the equipment, by pumping a solution of one of the deactivating materials through the apparatus for asufficient period of time to insure complete contact with all the sludge to be deactivated, which is usually accomplished in from to 30 minutes. Where a quantity of the sludge is obtained in cleaning out the equipment, it may be transferred to a suitable tank and agitated with a solution of the deactivator until complete deactivation is effected.

.The filter aids may be washed with a solution of the deactivating agent prior to their use in the process. They may be employed either before or after drying, for it has been found that they do not again become active even after being dried, or by being washed by the solutions that are filtered therethrough. H

The following examples are given to. illustrate the invention. The parts used are by weight.

EXAMPLE 1 tested for ignition activity by placing it on a filter .tivity as previously described.

paper, wetting it with a small quantity of tetraethyl lead and heating on a steam bath. No signs of ignition or of charring of the filter paper were noted even after 24 hours heating.

A sample of sludge which had been produced in a similar manner from the same batch of tetraethyl lead, except that the addition of copper oleate had been omitted, when tested for ac tivity as outlined above, ignited shortly after the sample was placed on the steam bath.

EXAMPLE 2 Approximately 1,000 parts of crude tetraethyl lead were placed in a suitable container provided with an agitator. About parts of water were added, and the sludge was precipitated by air blowing and collected in the water layer as disclosed in the previously mentioned application Ser. No. 393,680.

After the precipitation treatment was complete, the clear tetraethyl lead was decanted from the water layer in which the precipitated impurities were suspended. One part of ferric naphthenate was added to the aqueous sludge suspension, and the mixture was vigorously agitated for 30 minutes. The mixture was filtered, and a portion of the precipitated sludge was tested for ignition ac- It was found to be inactive. A sample of sludge taken before the ferric naphthenate was added was similarly tested and found to promote ignition of tetraethyl lead.

As illustrated in the above examples, the stabilizing agent may be added directly to the tetraalkyl lead to effect deactivation of the sludge that may be precipitated by air blowing or by any other process, or the sludge may be collected and separated from the tetraalkyl lead and stabilized by treatment with a suspension or solution of the deactivating metal salts.

When 10 parts of an active sludge were treated with 50 parts of a solution containing 0.1 part of one of the following oilsoluble salts of the carboxylic acids mentioned, completev deactivation of the sludge was effected so that when tested as described in Example 1 no ignition or charring was observed even after 72 hours of heating:-

tallow and other glycerides, and abietic acid,

memes" 5. Wherethe untreated sludge "employed in these tests wassubjected to the same ignition test as describedin Example: 1, it ignited shortly after being placed on thesteam bath.

As previously stated the invention may be employed to stabilize active filter aids which are to be used in tetraalkyl lead filtration. These materials may be washed in a solution of one of the deactivators and rendered suitable for tetraalkyl lead filtration. Thefollowing filter aidsas wellas a number of other materials of similar structure were wet with tetraethyl lead and placed on a steam bath asdescribed-' in- Example 1 above. All were found to initiate the ignition of tetraethyl lead. Ten parts of each-' of these materials were then agitated for several hours with 50 parts of a benzene solution of the copper i andiron salts of the carboxylic acids- Oi the concentrations given in the following table. Af-- tertheagitation period the solutions were-filtered and portions of thefilter cakes were wet with tetraethyl lead and placed on a steam bath. Results of these tests were as given in the following table:

M aterial Wash solution. 'g g None ignited;

.l% ferric stearate No decomposition. None Ignited:

0.2% ferric oleatc No decomposition. None Ignited.

Yellow lead oxide (N. F.

Do 0.5% cuprous naphthe- No decomponate. sition. Bismuth subnitrate None Ignited.

Do 0.2% ferrous palmitate. No decompo sition. Bismuth oxide (from hy- None Ignited.

drolysis of Bi(N03)3).

0.5% cubric oleate No decomposition.

Ferric oxide (anh). None Ignited.

Do 0.2% cupric naphthe- No decomponate. sition.

Activated Alumina None Ignited.

Do 0.2%cuprouspalmitate. No decomposition.

Dccolorizing charcoal None Ignited.

Do 0.2% ferric naphthe- No decomponate. sition.

EXAMPLE 3 Approximately 1,000 parts of crude tetraethyl lead and an equal weight of water were placed in a washer. Five parts of ferric stearate were then added and the sludge was precipitated and removed from the tetraethyl lead by the method disclosed in the copending application Ser. No. 393,680. After this operation was complete, the tetraethyl lead was removed by decantation, and the aqueous layer containing the sludge was filtered. A portion of the filter cake was then tested on the steam bath as described in Example 1. No decomposition or ignition of the tetraethyl lead was noted.

EXAMPLE 4 6 placed ina suitable tankor washer, and 2 parts ofcuprou's' n-aphthenate were dissolved therein. The contents or thetank were aerated and agitated fo -two hours as-disclosed in the copending' application Sen No. 393,680. After a settling period of a few minutes, the clear mixtureof lead alliyls was decanted from the aqueous layer and the aqueousmixture was filtered. A portion of the-filter cake was tested on the steambath as described in Example 1, except that theifil ter.

cake (sludge)' was wet with mixed lead alkyl compounds rather than with tetraethyl lead- No= decomposition or ignition of. the lead: .al-kyls was noted. A similar experiment was carried out P in whichno stabilizing agent was added. This sludge ignited the mixed. alkyls when the: stability test-was made.

A further use: of this: invention: will; be found in the-storage of'thef crudeitetraalkyl leads before they' are de-sludged. These deactivating copper and iron salts may be dissolved directly in. the. tetraalkyl lead. so that any sludg which precipitates out .on standing will be rendered. inactive-by contact with the deactivating agent;

1 In testing the: activity of the sludgesbefore or: afterrtreatmentiwith the deactivating. agents,.it will.be no.ted that tetraethyl or other. alkyl :lead was added. to the residues. This was to make sure there was sufiicient tetraalkyl lead-present to. ignite; under the. conditions employed if the sludge was not fully inactivated, for in some ins stances, it is possible: that; the amount of alkyl lead may be reduced to such a small amount that ignition might not be noted. While the elimination of the alkyl lead from the residues to such an extent does not ordinarily take place, the tests were made under conditions favoring ignition provided the sludge or filter aid was active.

This invention makes possible the deactivation of the ignitable sludges and residues occurring in the manufacture of tetraalkyl lead compounds and is of particular value in eliminating fire and explosion hazards involved in the removal and disposal of such sludges from the process and in overcoming the potential fire hazard arising from the collection of such sludges and precipitates which accumulate in various places in the processing equipment and which when exposed to air often ignite with considerable damage. The invention also permits the use of filter aids which, unless rendered inactive, tend to cause ignition of any absorbed tetraethyl lead when they are exposed to the air. Any other absorbent materials which for any reason may become saturated with tetraethyl lead in or about the plant in which it is being manufactured may be rendered inactive by washing or otherwise treating with stabilizers of the type described so that potential fire hazards may be removed as far as possible. Lagging on pipe which due to leaks may become saturated with tetraethyl lead and which have been known to cause its ignition can be inactivated by treating such lagging with the deactivating agents.

I claim:

l. The process for inhibiting the spontaneous ignition of tetraalkyl lead compounds adsorbed.

on sludges which are precipitated from crude tetraalkyl lead compounds and which sludges normally tend to cause spontaneous ignition of the tetraalkyl lead compounds adsorbed thereon when exposed to oxygen, which comprises incorporating with such sludges a compound of the group consisting of oil soluble copper salts of carboxylic acids and oil soluble iron salts of carboxylic acids.

2. The process for inhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spontaneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises incorporating with such sludges a compound of the group consisting of oil soluble copper salts of carboxylic acids and oil soluble iron salts of carboxylic acids.

3. The process for inhibiting the spontaneous ignition of tetraalkyl lead compounds adsorbed on solid materials which present a large surface area per unit volume and which normally tend to cause spontaneous ignition of the tetraalkyl lead compounds adsorbed thereon when exposed to oxygen, which comprises washing such materials with a solution of a compound of the group consisting of oil soluble copper salts of carboxylic acids and oil soluble iron salts of carboxylic 7 acids.

ignition of tetraethyl lead adsorbed on solid materials which present a large surface area per unit volume and which normally tend to cause spontaneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises incorporating with such materials an oil soluble copper naphthenate.

6. The process for inhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spontaneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises incorporating with such sludges an oil soluble copper naphthenate.

7. The process forinhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spontaneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises incorporating with such sludges an oil soluble copper oleate.

8. The process for inhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spontaneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises incorporating with such sludges an oil soluble iron stearate.

ADRIAN L. LINCI-I. 

